<!DOCTYPE html>
<style>
#mask {
  width: 200px;
  height: 200px;
  overflow: hidden;
  border-radius: 10px;
  border: 4px solid red;
  background-color: blue;
  position: relative;
  display: inline-block;
}

.content {
  width: 50px;
  height: 50px;
}

.composited {
  will-change: transform;
}
</style>

<p>Testing masks on compositing layers. Left and right columns should look the same.</p>
<div id="mask">
  <div class="content" style="left: 175px;top: 175px;background: black;position: absolute;"></div>
</div>
<div id="mask" class="composited" style="left: 50px">
  <div class="content" style="left: 175px;top: 175px;background: black;position: absolute;"></div>
</div>
